In the fields of the electronic and electrical industry and the automobile, aircraft and space industries, there is a strong demand in recent years for crystalline thermoplastic resins having high heat resistance of 300.degree. C. or higher in terms of melting point and moreover easy melt processability. Among these crystalline thermoplastic resins having high heat resistance, poly(arylene thioetherketones) (hereinafter abbreviated as "PTKs") are ultrahigh-heat-resistant aromatic polymers combining a high melting point of about 350.degree. C. with a high glass transition temperature of about 135.degree. C. There is hence a strong demand for provision of such polymers in the fields of frontier technologies, and the like.
PTKs can be produced by causing an alkali metal sulfide and a 4,4'-dihalobenzophenone to undergo a dehalogenation and sulfurization reaction in an organic amide solvent (Japanese Patent Application Laid-Open No. 4031/1989). However, PTKs involved a problem that when they are formed and processed by, for example, extrusion and subsequent stretching or sheet forming, it is considerably difficult from the technical viewpoint to apply these forming and processing methods thereto. This problem was believed to be attributed to the formation of coarse spherulites in a product formed by the extrusion owing to the too high crystallization.
In order to lower the crystallization rate of a PTK, the present inventor attempted to reduce the crystallinity and crystallization rate of the PTK by random copolymerization of its monomer with monomers of a kind different from the first-mentioned monomer. Namely, a 4,4'-dihalobenzophenone as a dihalogenated aromatic compound was combined with dihalobenzenes as dihalogenated aromatic compounds of a kind different from the 4,4'-dihalobenzophenone, respectively, followed by their reaction with an alkali metal sulfide, thereby producing an aromatic thioether ketone/thioether random copolymer somewhat lowered in crystallinity. However, it was difficult to obtain a random copolymer having a high molecular weight in the form of granules because the 4,4'-dihalobenzophenone and dihalobenzenes were different in reactivity from each other.
On the other hand, there has been proposed a block copolymer containing poly(arylene thioether-ketone) blocks and poly(arylene thioether) blocks (Japanese Patent Application Laid-Open No. 225527/1990). This block copolymer can be obtained by a process in which an alkali metal sulfide is reacted with a 4,4'-dihalobenzophenone in the presence of a poly(arylene thioether) prepolymer having reactive terminal groups to form a poly(arylene thioetherketone) block, or a process in which a poly(arylene thioether) prepolymer having reactive terminal groups is reacted with a poly(arylene thioether-ketone) prepolymer having reactive terminal groups. It is possible to collect a polymer moderately reduced in crystallization rate by suitably selecting reaction conditions in the production process. However, this block copolymer involves problems such that its melting point and glass transition temperature are lowered to a considerable extent compared with the PTK homopolymer, and its polymerization operation is complicated.